Article presents the influence of Nb content on structural properties of stress annealed Co21Fe64-xNbxB15 (x = 3, 5, 7) alloys has been studied using differential scanning calorimetery, in-situ length change measurements during annealing and x-ray diffraction. Results show that, increase of Nb content in the alloy increases the stability of the alloy against crystallization and is also responsible for higher elongation of the specimens. Crystallization leads to the formation of bcc Fe-Co nano-granular phase containing Co up to 38 % and affects the spin texture. Shailendra Singh Khinchi"Stress Annealed CoFeNbB Alloy : A Structural Study" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-1 | Issue-5 , August 2017, URL: http://www.ijtsrd.com/papers/ijtsrd2271.pdf http://www.ijtsrd.com/physics/engineering-physics/2271/stress-annealed-cofenbb-alloy--a-structural-study/shailendra-singh-khinchi
Stress Annealed CoFeNbB Alloy : A Structural Study
1. @ IJTSRD | Available Online @ www.ijtsrd.com | Volume – 1 | Issue – 5 Page: 235
ISSN No: 2456 - 6470 | www.ijtsrd.com | Volume - 1 | Issue – 5
International Journal of Trend in Scientific
Research and Development (IJTSRD)
UGC Approved International Open Access Journal
Stress annealed CoFeNbB alloy : A structural study
Shailendra Singh Khinchi
Department of Applied Physics,
Institute of Engineering and Technology
Devi Ahilya University, Indore, India
ABSTRACT
Article presents the influence of Nb content on
structural properties of stress annealed Co21Fe64-
xNbxB15 (x = 3, 5, 7) alloys has been studied using
differential scanning calorimetery, in-situ length
change measurements during annealing and x-ray
diffraction. Results show that, increase of Nb content
in the alloy increases the stability of the alloy against
crystallization and is also responsible for higher
elongation of the specimens. Crystallization leads to
the formation of bcc Fe-Co nano-granular phase
containing Co up to 38 % and affects the spin texture.
1. INTRODUCTION
Stress annealing of magnetic materials is known to
induce significant uniaxial magnetic anisotropy. In
materials consisting of α-Fe type nanoparticles
dispersed in an amorphous matrix, this treatment can
result in a strong anisotropy. In FINEMET type alloys
(FeSiBNbCu), the stress induced anisotropy is
perpandicular (KU<0) to tensile stress direction [1]
and strong (~10 J.m-3
MPa-1
) whereas Co substitution
truns it to longitudinal direction (KU>0) for 20 to 50%
Co substituted to Fe [8]. The sign of uniaxial
anisotropy coefficient is generally the same as that of
the magnetostriction coefficient of the nanograins
However, for some alloys (FeZrB NANOPERM or 80%
Co substituted FINEMET) the direction of the
anosotropy is opposite to expectations [2]. It seems
that this phenomenon is linked to the viscous
behaviour of the amorphous phase in the supercooled
liquid region, i.e., between the glass transion and
crystallisation temperatures (Tg and resp. TX). To go
insight this problem, it is necessary to study alloys
with different TX-Tg values. The influence of Nb
content on structural properties of stress annealed
Co21Fe64-xNbxB15 (x = 3, 5, 7) alloys has been studied
using differential scanning calorimetery (DSC), in-
situ length change measurements during annealing
and x-ray diffraction (XRD).
2. EXPERIMENTAL DETAILS
Ribbons of nominal composition Co21Fe64-xNbxB15
with x = 3, 5, 7 (about 20 µm thick and 10 mm wide)
were prepared using a planar flow casting technique
on copper wheel. First crystallization peak
temperature (TX1) was determined using DSC
measurements performed at a heating rate of 20
o
C/min. Specimens were annealed at 450, 500 and 550
0
C with applied stress of 200 MPa for 1 h in the
protective atmosphere of flowing Ar. The elongation
(L) of the 1 m long ribbons was measured during
annealing by means of a Linear Variable Differential
Transformer. Recording of L and temperature was
performed using a PC linked GPIB standard card as a
function of time at a rate of 1 point/s during the whole
thermal treatment (heating at 10 K/min, plateau at TA,
cooling at 10 K/min). Cu-K XRD measurements
were done at room temperature, and were analyzed
using pseudo-Voigt line profile to obtain lattice
parameter (a) and average grain size (D) and the
volume fraction of the nanograins (Vx). Transmission
Mössbauer spectra were recorded at room
temperature, using 57
Co:Rh source.
2. International Journal of Trend in Scientific Research and Development (IJTSRD) ISSN: 2456-6470
@ IJTSRD | Available Online @ www.ijtsrd.com | Volume – 1 | Issue – 5 Page: 236
3. RESULT AND DISCUSSION
TX1 for samples with x = 3, 5 and 7 are respectively
408, 442 and 475 0
C, showing that increase of Nb
content increases the stability of the alloy against
crystallization. Figure 4 shows the elongation (L) for
Co21Fe64-xNbxB15 during the same annealing cycle.
Perusal of figure 4 shows that, higher the Nb content
in the alloy higher is the elongation of the alloy.
TX1 for samples with x = 3, 5, and 7 are respectively
408, 442 and 475 °C, showing that increase of Nb
content increases the stability of the alloy against
crystallization. Fig. 1 shows the elongation (Δl) for
Co21Fe64-xNbxB15 during the annealing cycle
(mentioned above). Perusal of Fig. 4 shows that,
higher the Nb content in the alloy higher is the
elongation of the alloy. Tg is deduced from the plot of
dl/dt, which is the viscous flow speed. Below Tg, this
speed is small and equal for all samples (0.5 mm/min).
After correction of the thermal dilatation (~ 510-6
K-
1
), the constant viscosity (~ 0.510-12
Pa.s) is
attributed to short range ordering [3].
Maximum flow speed was 60 mm/min for x=7% and
the viscosity felt down to 4·10-9 Pa.s at 500 °C. The
higher elongation is observed for the same sample due
to the increase of crystallization temperature,
enhancing the super cooled liquid region. It is
important to note that application of stress modifies
the total free energy of the metastable amorphous
phase resulting in a lower Tg compared to
measurements performed by DSC.
XRD data shows that the crystallization of the
specimens starts after annealing at 450 o
C with 200
MPa stress (except for the specimen with x= 7, where
crystallization starts after annealing of the specimen
after 500 o
C) showing a co-existence of the crystalline
phase and the residual amorphous matrix.
Figure 1: Elongation (L) for Co21Fe64-xNbxB15
alloys after annealing at 500 oC
Table 1 depicts the Scherrer’s crystallite size (D),
lattice parameter (a) and volume fraction of the nano-
grains (Vx) obtained by fitting the XRD data. In the
early stage of crystallisation (450°C), lattice
parameters are rather high which suggests the
precipitation of bcc Fe nano-granular phase with
rather low Co content (15%) and a substantial lattice
expansion that can be due to the presence of Nb solute
atoms. As the annealing temperature increases, lattice
parameters become consistent with bulk values and
indicate a Co content of 15 - 20%, 30%, and 35% for
x=3, 5, and 7 respectively. As Nb content in the
specimen increases, for same annealing temperature
‘D’ is systematically smaller for the sample
containing higher Nb content. Vx shows similar
behavior for the studied samples. Behavior of D and
Vx can be understood in terms of increase of TX1
values with increase of Nb content in the alloy.
0 20 40 60 80 100 120 140 160 180
0
5
10
15
20
25
30
35
40
45
50
Ta
= 500°C
1 hour
= 200MPa
Temperature(°C)
l(mm)
Time (min.)
Co21
Fe61
Nb3
B15
Co21
Fe59
Nb5
B15
Co21
Fe57
Nb7
B15 0
50
100
150
200
250
300
350
400
450
500
550
3. International Journal of Trend in Scientific Research and Development (IJTSRD) ISSN: 2456-6470
@ IJTSRD | Available Online @ www.ijtsrd.com | Volume – 1 | Issue – 5 Page: 237
Table 1: Thermodynamical (TX, Tg) and structural (a, D and Vx ) parameters for stress
annealed Co21Fe64-xNbxB15 specimens.
4. CONCLUSION
In conclusion, higher Nb content in the alloy increases
the stability of the alloy against crystallization and is
also responsible for the obtained higher elongation of
the alloy through the enhancement of the super cooled
liquid region. Crystallization of the studied alloys
affects their spin texture in the amorphous matrix
showing that higher the elongation, the more spin
texture is out of plane.
REFERENCES
[1] A. A.Glaser and N. M. Kleynerman and V. A.
Lukshina and A. P. Patapov and V. V. Serikov,
Phys.Met. Metal. 72 (1991) 53
[2] Zs. Gercsi, S. N. Kane, J. M. Greneche, L. K.
Varga and F. Mazaleyrat, Phys. Stat. Sol. (C) 1
(2004) 3607
[3] G. Vlasak, P. Svec and P. Duha, Mat. Sci. Eng. A,
304-306 (2001) 472.
[4] A. Gupta, S. N. Kane, N. Bhagat and T. Kulik, J.
Magn. Magn. Mater. 254-255 (2003) 492.
[5] C. E. Johnson, M. S. Ridout, T.E. Cranshow and
P. E. Madsen, Phys. Rev. Lett. 6 (1961) 450.
Nb
(at.%)
TX/Tg
(°C)
Ann. Temp
(°C)
L
(mm)
a (nm)
0.0001
D (nm)
2
Vx (%)
2
3
408
342
450 10.4 0.2869 30 45
500 14.1 0.2867 35 55
550 17.9 0.2867 38 55
5
442
384
450 12.9 0.2870 15 15
500 13.4 0.2869 16 45
550 27.2 0.2864 15 60
7
475
397
450 10.7 - - -
500 45.4 0.2862 10 25
550 >50 0.2862 15 55
![@ IJTSRD | Available Online @ www.ijtsrd.com | Volume – 1 | Issue – 5 Page: 235
ISSN No: 2456 - 6470 | www.ijtsrd.com | Volume - 1 | Issue – 5
International Journal of Trend in Scientific
Research and Development (IJTSRD)
UGC Approved International Open Access Journal
Stress annealed CoFeNbB alloy : A structural study
Shailendra Singh Khinchi
Department of Applied Physics,
Institute of Engineering and Technology
Devi Ahilya University, Indore, India
ABSTRACT
Article presents the influence of Nb content on
structural properties of stress annealed Co21Fe64-
xNbxB15 (x = 3, 5, 7) alloys has been studied using
differential scanning calorimetery, in-situ length
change measurements during annealing and x-ray
diffraction. Results show that, increase of Nb content
in the alloy increases the stability of the alloy against
crystallization and is also responsible for higher
elongation of the specimens. Crystallization leads to
the formation of bcc Fe-Co nano-granular phase
containing Co up to 38 % and affects the spin texture.
1. INTRODUCTION
Stress annealing of magnetic materials is known to
induce significant uniaxial magnetic anisotropy. In
materials consisting of α-Fe type nanoparticles
dispersed in an amorphous matrix, this treatment can
result in a strong anisotropy. In FINEMET type alloys
(FeSiBNbCu), the stress induced anisotropy is
perpandicular (KU<0) to tensile stress direction [1]
and strong (~10 J.m-3
MPa-1
) whereas Co substitution
truns it to longitudinal direction (KU>0) for 20 to 50%
Co substituted to Fe [8]. The sign of uniaxial
anisotropy coefficient is generally the same as that of
the magnetostriction coefficient of the nanograins
However, for some alloys (FeZrB NANOPERM or 80%
Co substituted FINEMET) the direction of the
anosotropy is opposite to expectations [2]. It seems
that this phenomenon is linked to the viscous
behaviour of the amorphous phase in the supercooled
liquid region, i.e., between the glass transion and
crystallisation temperatures (Tg and resp. TX). To go
insight this problem, it is necessary to study alloys
with different TX-Tg values. The influence of Nb
content on structural properties of stress annealed
Co21Fe64-xNbxB15 (x = 3, 5, 7) alloys has been studied
using differential scanning calorimetery (DSC), in-
situ length change measurements during annealing
and x-ray diffraction (XRD).
2. EXPERIMENTAL DETAILS
Ribbons of nominal composition Co21Fe64-xNbxB15
with x = 3, 5, 7 (about 20 µm thick and 10 mm wide)
were prepared using a planar flow casting technique
on copper wheel. First crystallization peak
temperature (TX1) was determined using DSC
measurements performed at a heating rate of 20
o
C/min. Specimens were annealed at 450, 500 and 550
0
C with applied stress of 200 MPa for 1 h in the
protective atmosphere of flowing Ar. The elongation
(L) of the 1 m long ribbons was measured during
annealing by means of a Linear Variable Differential
Transformer. Recording of L and temperature was
performed using a PC linked GPIB standard card as a
function of time at a rate of 1 point/s during the whole
thermal treatment (heating at 10 K/min, plateau at TA,
cooling at 10 K/min). Cu-K XRD measurements
were done at room temperature, and were analyzed
using pseudo-Voigt line profile to obtain lattice
parameter (a) and average grain size (D) and the
volume fraction of the nanograins (Vx). Transmission
Mössbauer spectra were recorded at room
temperature, using 57
Co:Rh source.](https://image.slidesharecdn.com/36stressannealedcofenbballoy-180809051919/85/Stress-Annealed-CoFeNbB-Alloy-A-Structural-Study-1-320.jpg)
![International Journal of Trend in Scientific Research and Development (IJTSRD) ISSN: 2456-6470
@ IJTSRD | Available Online @ www.ijtsrd.com | Volume – 1 | Issue – 5 Page: 236
3. RESULT AND DISCUSSION
TX1 for samples with x = 3, 5 and 7 are respectively
408, 442 and 475 0
C, showing that increase of Nb
content increases the stability of the alloy against
crystallization. Figure 4 shows the elongation (L) for
Co21Fe64-xNbxB15 during the same annealing cycle.
Perusal of figure 4 shows that, higher the Nb content
in the alloy higher is the elongation of the alloy.
TX1 for samples with x = 3, 5, and 7 are respectively
408, 442 and 475 °C, showing that increase of Nb
content increases the stability of the alloy against
crystallization. Fig. 1 shows the elongation (Δl) for
Co21Fe64-xNbxB15 during the annealing cycle
(mentioned above). Perusal of Fig. 4 shows that,
higher the Nb content in the alloy higher is the
elongation of the alloy. Tg is deduced from the plot of
dl/dt, which is the viscous flow speed. Below Tg, this
speed is small and equal for all samples (0.5 mm/min).
After correction of the thermal dilatation (~ 510-6
K-
1
), the constant viscosity (~ 0.510-12
Pa.s) is
attributed to short range ordering [3].
Maximum flow speed was 60 mm/min for x=7% and
the viscosity felt down to 4·10-9 Pa.s at 500 °C. The
higher elongation is observed for the same sample due
to the increase of crystallization temperature,
enhancing the super cooled liquid region. It is
important to note that application of stress modifies
the total free energy of the metastable amorphous
phase resulting in a lower Tg compared to
measurements performed by DSC.
XRD data shows that the crystallization of the
specimens starts after annealing at 450 o
C with 200
MPa stress (except for the specimen with x= 7, where
crystallization starts after annealing of the specimen
after 500 o
C) showing a co-existence of the crystalline
phase and the residual amorphous matrix.
Figure 1: Elongation (L) for Co21Fe64-xNbxB15
alloys after annealing at 500 oC
Table 1 depicts the Scherrer’s crystallite size (D),
lattice parameter (a) and volume fraction of the nano-
grains (Vx) obtained by fitting the XRD data. In the
early stage of crystallisation (450°C), lattice
parameters are rather high which suggests the
precipitation of bcc Fe nano-granular phase with
rather low Co content (15%) and a substantial lattice
expansion that can be due to the presence of Nb solute
atoms. As the annealing temperature increases, lattice
parameters become consistent with bulk values and
indicate a Co content of 15 - 20%, 30%, and 35% for
x=3, 5, and 7 respectively. As Nb content in the
specimen increases, for same annealing temperature
‘D’ is systematically smaller for the sample
containing higher Nb content. Vx shows similar
behavior for the studied samples. Behavior of D and
Vx can be understood in terms of increase of TX1
values with increase of Nb content in the alloy.
0 20 40 60 80 100 120 140 160 180
0
5
10
15
20
25
30
35
40
45
50
Ta
= 500°C
1 hour
= 200MPa
Temperature(°C)
l(mm)
Time (min.)
Co21
Fe61
Nb3
B15
Co21
Fe59
Nb5
B15
Co21
Fe57
Nb7
B15 0
50
100
150
200
250
300
350
400
450
500
550](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)